At present, a Long Term Evolution (LTE) system adopts a centralized network control manner, that is, uplink data and downlink data of terminal device are sent and received under the control of a network. As shown in FIG. 1, communication between terminal devices is forwarded and controlled by a network, there is no direct communication link between the terminal devices, and the terminal device is not allowed to send uplink data by itself.
As shown in FIG. 2, in a device-to-device (D2D) communication mode, terminal devices can directly communicate with each other without transmission or forwarding performed by a device such as an evolved NodeB (referred to as an eNB). The direct communication link can be established under the control or with the assistance of a network. D2D communication between terminal devices may be performed based on a D2D discovery process for terminal devices that are close to each other. In this case, terminal device located at a remote end may directly communicate with relay (English: Relay) terminal device in the D2D communication mode, and the relay terminal device is directly connected to the evolved NodeB in a cellular manner. The remote terminal device may directly communicate with the evolved NodeB in a cellular communication manner, or may perform relay communication with the evolved NodeB by using the relay terminal device.
In the prior art, for terminal device having two communication modes, that is, a cellular module and a D2D communications module, a radio link failure (RLF) is likely to occur in both a direct cellular communication process and a D2D relay communication process. When a radio link failure occurs in cellular communication or D2D communication of the terminal device, no corresponding communication control solution is available in the prior art to ensure effective communication of the terminal device.